A new Docker version was developed to be used locally. You can download and check the instructions on the hub docker page (https://hub.docker.com/repository/docker/dbpedia/dbpedia-spotlight). Please, any questions don’t hesitate to publish it (we are working in some improvements).
And, the https://www.dbpedia-spotlight.org/api page is the API page for the DBpedia Spotlight English language (Also, it is intended to add two or three additional languages).
I hope this information could help you and please, I would be happy to hear any feedback.